284 BULLETIN OF THE BUREAU OF FISHERIES 



Rhiacalanus nasutus Glesbreclit 



This is a typically oceanic species, warm temperate in its relationship to tem- 

 perature, and wide ranging in all three great oceans. It has been recorded widely 

 in the eastern Pacific (Giesbrecht, 1892; Esterly, 1905), in the Malay Archipelago 

 (Andrew Scott, 1909 52 ), at several localities in the northern part of the Indian 

 Ocean (Thompson and Scott, 1903; Wolfenden, 1905), and at the mouth of the 

 Red Sea (A. Scott, 1902). In the Atlantic it is known from latitude 35° 10' S., in the 

 south (Wolfenden, 1911), to Denmark Strait, the sea south of Iceland, the neighbor- 

 hood of the Faroes, the Norwegian sea, and the northern part of the North Sea in 

 the north. Farran (1910) and With (1915), who have summarized what is known 

 of its distribution, have both pointed out that in the northeastern part of its area 

 of occurrence its range is coterminous with the ebbings and Sowings of the highly 

 saline and comparatively warm waters of the Atlantic current. This applies equally 

 off the Atlantic seaboard of North America, where it has been taken outside the 

 continental edge off Chesapeake Bay, off Delaware Bay, and off New York in the 

 summer of 1913 (stations 10064, 10071, and 10076); off Georges Bank, July, 1914 

 (stations 10218 and 10220); off Cape Sable; off Sable Island; and off the mouth 

 of the Laurentian Channel between the Nova Scotian and Newfoundland Banks, 

 June-July, 1915 (Willey, 1919, 7 stations) ; also east of the Grand Banks by the 

 Michael Sars (Murray and Hjort, 1912, p. 654). 



Within the Gulf of Maine R. nasutus has much the same status as its close rela- 

 tive R. comutus (p. 283), there being 10 records, all but one of them in the peripheral 

 belt, around which they are scattered from Browns Bank and off Yarmouth, Nova 

 Scotia, to off the tip of Cape Cod, a distribution quite typical for any planktonic 

 animal reaching the gulf as an immigrant from the Atlantic basin and unable to 

 survive long or to reproduce itself there. 



The geographic locations of the stations where R. nasutus was taken (fig. 72) 

 are also interesting in pointing to the upper 100 meters or so as the stratum in which 

 it enters, for if it drifted into the gulf in the underlying waters it might be expected 

 to follow the branches of the basin, as do the bathypelagic chretognaths Eukrohnia 

 hamata (p. 328) and Sagitta maxima (p. 324), instead of circling along and inside 

 the 100-meter contour. 



Farran (1910) and With (1915) have described the vertical range of this species 

 as uniform from the surface down to 1,800 meters. Most of the captures listed by 

 Willey (1919) in Canadian waters were in open vertical hauls from depths of 200 to 

 375 meters; once on the surface. The Michael Sars record just mentioned was in a 

 closing net at 950 to 525 meters. The captures within the Gulf of Maine have all 

 been in open nets — horizontal (station 10225) or vertical — from depths of from 48-0 

 down to 240-0 meters; none from the surface. 



The Gulf of Maine records for R. nasutus are for the months of March (three), 

 April (two) , May (four) , and one for July ; M but with so few records it is questionable, 

 whether this seasonal periodocity actually means that R. nasutus is more apt to enter 



63 He uses the name Rhincalanus gigas Brady for it. 



"In addition to the stations listed in the tables, (p. 297), R. nasutus was taken at station 10225 on July 23, 1914, and at 

 stations 10272 and 10273 on May 10, 1915. 



